Medical tunneling device and method

ABSTRACT

A medical device assembly includes a tunneler having a proximal end and a distal end and a carrier element fixed to the distal end of the tunneler. In various embodiments the carrier element is configured to be slidably disposed within a lead connection lumen. In various embodiments the carrier element includes a plurality of recesses configured to engage a lead extension set screw. In various embodiments the carrier element can freely rotate relative to the rest of the tunneler.

PRIORITY

This application claims the benefit of U.S. Provisional Application No.61/480,599 entitled “MEDICAL TUNNELING DEVICE AND METHOD” filed on Apr.29, 2011, and the benefit of U.S. Provisional Application No. 61/480,594entitled “MEDICAL TUNNELING DEVICE AND METHOD MEDICAL TUNNELING DEVICEWITH SWIVEL AND METHOD” filed on Apr. 29, 2011, the entire contents ofeach of which are incorporated herein by reference.

FIELD

This disclosure relates, inter alia, to implantable medical devices.More particularly, it relates to implantable medical devices and systemsemploying lead extensions and placement of implanted lead extensionswith a tunneling device.

BACKGROUND

Placement of lead extensions in a patient may be required in a number ofsituations, such as placement of a medical device where the leadextension electrically connects an implantable electrical medical deviceto an electrical lead.

The use of lead extensions can serve multiple purposes. For example,lead extensions can electrically bridge the distance between a suitableimplant site for an implantable pulse generator (IPG) and a leadimplanted at tissue targeted for stimulation or sensing, where the leadalone may not be long enough. In some cases, an IPG may be implanted inthe chest and a lead may be specifically configured to be implanted inthe brain and accordingly the lead may be particularly thin and haveexternal material suited for contacting brain matter. These designconsiderations may render the lead unsuitable for bridging a connectionthrough the neck, as a lead that spans the neck may need to be durable,robust, extendable, and flexible enough to survive the everydayrotations, articulations, and extensions of the neck. In some cases, thelead extension may be specially configured to handle the neckenvironment (e.g., by being thicker and more flexible) while the leadmay be specifically configured to handle the brain environment (e.g.,thin enough to minimize interference with brain tissue and rigid enoughto maintain implant position and orientation).

Implantation of lead extensions bridging the head and chest may becomplicated by the lead extensions tangling when pulled though asubcutaneous tunnel between the head and chest. Tangling of the leadextension can increase the chances of the extension catching onsomething and/or requiring an increased pull force and/or a remedialsurgical technique.

Sometimes carrier units are used to temporarily house a distal endconnector of the lead extension to secure the lead extension to thetunneler and allow the tunneler to pull the lead extension through thesubcutaneous tunnel. However, the carrier element in these cases wrapsaround distal end connector, which can make for a larger profile of theassembly as it is pulled through the subcutaneous tunnel, increasingresistance within the tunnel.

In some patients, resistance can be experienced while removing thetunneling device with the lead extension. Excessive force to remove thetunneling device with the lead extension can result in carrier failure.

SUMMARY

The present disclosure describes, among other things, apparatuses andmethods that provide for robust placement of a lead extension in apatient.

Various embodiments concern a medical device assembly including atunneler having a proximal end and a distal end and a carrier elementfixed to the distal end of the tunneler. The carrier element isconfigured to be slidably disposed within a lead connection lumen. Thecarrier element includes a plurality of recesses configured to engage alead extension set screw.

Various embodiments concern a medical device assembly including atunneler having a proximal end and a distal end and a first and secondcarrier element fixed to the distal end of the tunneler. The firstcarrier element is configured to be slidably disposed within a firstlead connection lumen. The first carrier element includes a plurality ofrecesses configured to engage a first lead extension set screw. Thesecond carrier element is configured to be slidably disposed within asecond lead connection lumen. The second carrier element includes aplurality of recesses configured to engage a second lead extension setscrew.

Various embodiments concern a method comprising passing a tunneler froma first opening to a second opening in a patient, disposing a distal endcarrier portion of the tunneler into a lead connection lumen of a leadextension, the lead extension having a set screw proximal to the leadconnection lumen, and fixing the lead extension to the carrier portionwith the set screw. The method includes pulling the tunneler andattached lead extension from the second opening to the first opening inthe patient so that the lead extension extends between the secondopening and the first opening in the patient, and removing the leadextension from the carrier portion. The method includes fixing the leadextension to the carrier portion with the set screw.

Various embodiments concern a method comprising: passing a tunneler froma first opening to a second opening in a patient, a subcutaneous tunnelbeing made by the passing of the tunneler; disposing a distal endcarrier portion of the tunneler into a lead connection lumen of a leadextension, the lead extension having a set screw; fixing the leadextension to the distal end carrier portion with the set screw; pullingthe tunneler and attached lead extension from the second opening to thefirst opening in the patient so that the lead extension extends betweenthe second opening and the first opening in the patient; unfixing thelead extension from the distal end carrier portion with the set screw;removing the distal end carrier portion from the lead connection lumen;and connecting a lead to the lead extension by inserting a proximal endof the lead into the lead connection lumen and securing the lead to thelead extension with the set screw, the connecting of the lead to thelead extension completing at least one electrical connection between oneor more electrical conductors of the lead extension and one or moreelectrodes on the distal end of the lead.

Some of the method embodiments further comprise removing a tunneling tipfrom the distal end of the tunneler after the passing step but beforethe disposing step, the tunneling tip configured to make the tunnel insubcutaneous tissue; and fixing the carrier portion to the distal end ofthe tunneler after the removing step.

In some of the method embodiments, fixing the lead extension to thedistal end carrier portion comprises engaging the distal end carrierportion with the set screw; and unfixing the lead extension from thedistal end carrier portion comprises disengaging the distal end carrierportion from the set screw.

In some of the method embodiments, the fixing step comprises fixing thelead extension to the distal end carrier portion with two or more setscrews engaging the distal end carrier portion; and unfixing comprisesreleasing the two or more set screws from contact with the distal endcarrier portion.

In some of the method embodiments, the tunneler creates one or both ofthe first opening and the second opening.

In some of the method embodiments, the distal end carrier portioncomprises a first carrier element and a second carrier element, thefirst and second carrier elements connected. to a common hub; the leadextension comprises a first lead extension having a first leadconnection lumen and a second lead extension having a second leadconnection lumen; the lead comprises a first lead having a proximal endand a distal end and a second lead having a proximal end and a distalend; disposing comprises disposing the first carrier element in thefirst lead connection lumen and disposing the second carrier element inthe second lead connection lumen; and pulling the tunneler and attachedlead extension comprises pulling the tunneler and both of the first andsecond lead extensions from the second opening to the first opening inthe patient so that the first and second lead extensions extend betweenthe second opening and the first opening in the patient; unfixing thelead extension comprises unfixing the first and second lead extensionsfrom the first and the second carrier elements; removing the distal endcarrier portion comprises removing the first and the second carrierelements from the first and the second lead extension lumens; andconnecting the lead to the lead extension comprises inserting theproximal end of the first lead into the first lead connection lumen,securing the first lead to the first lead extension with a first setscrew, inserting the proximal end of the second lead into the secondlead connection lumen, and securing the second lead to the second leadextension with a second set screw.

Various embodiments concern a medical device assembly comprising: a leadhaving a proximal end and a distal end, the distal end having one ormore electrodes on the distal end of the lead; a lead extension having aproximal end and a distal end, the distal end of the lead extensionhaving a lead connection lumen and one or more electrical contacts, thelead and the lead extension configured such that the proximal end of thelead can be inserted into the lead connection lumen to complete at leastone electrical connection between the one or more electrical contacts ofthe lead extension and the one or more electrodes of the lead, the leadextension configured to be securable to the lead when the proximal endof the lead is within the lead connection lumen; a tunneler having aproximal end and a distal end, the tunneler comprising a tip configuredto make a subcutaneous tunnel, the tip either fixed or fixable to thedistal end of the tunneler; and a carrier element either fixed orfixable to the distal end of the tunneler, wherein the carrier elementis configured to be slidably disposed within the lead connection lumenand the lead extension is configured to be securable to the carrierelement when the carrier element is within the lead connection lumen.

In some device embodiments, the lead extension comprises one or more setscrews; the lead extension is configured to be securable to the carrierelement by engagement between the one or more set screws and the carrierelement; and the lead extension is configured to be securable to thelead by engagement between the one or more set screws and the proximalend of the lead.

In some device embodiments, the carrier element comprises one or morerecesses and the lead extension comprises one or more set screws,wherein the lead extension is configured to be securable to the carrierelement by engagement between the one or more set screws and the one ormore recesses when the carrier element is within the lead connectionlumen.

In some device embodiments, the one or more recesses comprises aplurality of recesses, the one or more set screws comprises a pluralityof set screws, and the plurality of set screws and the plurality ofrecesses are configured such that the plurality of set screwsrespectively align with the plurality of recesses when the carrierelement is within the lead connection lumen.

In some device embodiments, at least one of the one or more recesses hasa planar bottom surface that is engaged by at least one of the one ormore set screws. In some of the device embodiments, the carrier elementis threadedly fixable to the distal end of the tunneler.

In some of the device embodiments, the carrier element is permanentlyfixed to the distal end of the tunneler.

In some of the device embodiments, the carrier element is an elongatedrod.

In some of the device embodiments, the carrier element circumferentiallyfills the entire lead connection lumen when the carrier element iswithin the lead connection lumen.

In some of the device embodiments, the tip is configured to be removablefrom the tunneler.

In some of the device embodiments, the carrier element is able to befixed to the tunneler only when the tip has been removed from thetunneler.

In some of the device embodiments, the tip is on a distal end of thecarrier element.

In some of the device embodiments, the carrier element comprises a firstcarrier element and a second carrier element both fixed or fixable tothe distal end of the tunneler; the lead extension comprises a firstlead extension securable to the first carrier element and a second leadextension securable to the second carrier element; the lead connectionlumen comprises a first lead connection lumen and a second leadconnection lumen; and the first carrier element is configured to beslidably disposed within the first lead connection lumen and the secondcarrier element is configured to be slidably disposed within the secondlead connection lumen to facilitate securement between the first leadextension and the first carrier element and between the second leadextension and the second carrier element.

In some of the device embodiments, at least a portion of the firstcarrier element and second carrier element are parallel extendingelongated rods.

In some of the device embodiments, the first carrier element and thesecond carrier element are fixed to a common hub element and the commonhub element is fixed or fixable to the distal end of the tunneler.

In some of the device embodiments, the first carrier element comprisesone or more recesses; the first lead extension comprises one or morefirst lead extension set screws configured to respectively engage theone or more recesses of the first carrier element to facilitatesecurement between the first lead extension and the first carrierelement; the second carrier element comprises one or more recesses; andthe second lead extension comprises one or more second lead extensionset screws configured to respectively engage the one or more recesses ofthe second carrier element to facilitate securement between the secondlead extension and the second carrier element.

By providing the carrier portion of the tunneler that can be disposedinto a lead connection lumen of a lead extension, a robust medicaldevice assembly is formed and can place a lead extension in a patientwhile reducing the force required to withdraw the medical deviceassembly through the subcutaneous tunnel as compared to larger profiledevices and techniques. These and various other features and advantageswill be apparent from a reading of the following detailed description.

In various embodiments, a medical device assembly includes a tunnelerhaving a proximal end and a distal end and a swivel element having aswivel proximal end and a swivel distal end. The swivel proximal end isfixed to the distal end of the tunneler and freely rotates about thedistal end of the tunneler. The swivel distal end includes a male orfemale threaded end.

In some other embodiments, a medical device assembly includes a tunnelerhaving a proximal end and a distal end and a swivel element having aswivel proximal end and a swivel distal end. The swivel proximal end isfixed to the distal end of the tunneler and freely rotates about thedistal end of the tunneler. The swivel distal end includes a male orfemale threaded end. A medical device is threadedly attached to theswivel distal end.

Various embodiments concern a method of passing a tunneler from a firstopening to a second opening in a patient. The tunneler includes a swivelelement fixed to a distal end of the tunneler. The swivel element freelyrotates about the distal end of the tunneler. The method includesrotating the swivel element to attach a medical device and pulling themedical device from the second opening to the first opening in thepatient with the tunneler.

By providing the swivel element on the tunneler, a medical device (e.g.,lead extension) can be easily and robustly attached to the swivel endand can place the medical device in a patient. The use of a swivel endin this manner can reduce twisting, deformation, and/or entanglement ofthe implanted lead extension thereby reducing the chance that a largepulling force will be required to withdraw the medical device assemblythrough the patient.

Various embodiments concern a medical device assembly for implanting anelongated lead element in a subcutaneous tunnel including a tunnelerhaving a proximal end and a distal end, the tunneler configured to spanthe subcutaneous tunnel, a swivel element having a proximal end and adistal end, the proximal end rotatably fixed or fixable to the distalend of the tunneler and freely rotatable about the distal end of thetunneler, the distal end of the swivel element comprises a male orfemale threaded end, and a carrier element comprising a male or femalethreaded end configured to engage with the male or female threaded endof the swivel element, the carrier element configured to attach to theelongated lead element to securely link the elongated lead element tothe tunneler, the swivel element configured to permit rotation betweenthe carrier element and the tunneler. In some medical device assemblyembodiments, the tunneler comprises either one of a male couplingelement or a female connection element, and the swivel element comprisesthe other of the male coupling element or the female connection element,the male coupling element and the female connection element configuredto slidably engage to connect the swivel element to the tunneler.

In some medical device assembly embodiments, the male coupling elementcomprises a recess or groove about a perimeter of the male couplingelement and the female connection element comprises a detent configuredto engage with the recess or groove and fix the swivel element to thetunneler white permitting rotation between the tunneler and the carrierelement.

Some medical device assembly embodiments include a tunneling tipconfigured to make the subcutaneous tunnel. In some embodiments, thetunneling tip comprises a male or female threaded end configured toengage with the male or female threaded end of the swivel element, thetunneling tip configured to make the subcutaneous tunnel when attachedto the distal end of the swivel element. In some embodiments, thetunneling tip is fixable to the distal end of the tunneler when theswivel element is not attached to the distal end of the tunneler.

In some medical device assembly embodiments, the carrier elementcomprises a holder, the holder configured to hold an end of the leadextension within the holder.

In some medical device assembly embodiments, the swivel elementcomprises a roughened or knurled exterior surface.

In some medical device assembly embodiments, the tunneler is a solidmetal rod.

In some medical device assembly embodiments, the elongated lead elementis a lead extension having a proximal end and a distal end, the proximalend configured to plug into an electrical implantable medical device andthe distal end having a receptacle and a lumen, the lumen configured toaccept a distal end of a lead.

Various embodiments concern a method of implanting an elongated leadelement within a subcutaneous tunnel comprising: passing a tunneler froma first opening to a second opening in a patient, a subcutaneous tunnelbeing made by the passing of the tunneler, detaching a tunneling tipwhile a distal end of the tunneler extends out of the second opening,attaching a carrier element to a swivel element by twisting the swivelelement, the swivel element connected to the tunneler, attaching theelongated lead element to the carrier element, the swivel elementconfigured to securely link the elongated lead element to the tunnelerwhile permitting rotation between the elongated lead element and thetunneler, and pulling the elongated lead element from the second openingto the first opening with the tunneler so that the elongated leadelement extends from the second opening to the first opening in thesubcutaneous tunnel.

In some method embodiments, detaching the tunneling tip comprisingdisengaging the tunneling tip from threading of the swivel element bytwisting the swivel element, and attaching the carrier element to theswivel element comprises engaging the threading of the swivel elementwith threading of the carrier element.

In some medical device assembly embodiments, the tunneling tip isdirectly attached to the swivel element and the swivel element isdirectly attached to the tunneler during the passing step and detachingthe tunneling tip comprises detaching the tunneling tip from the swivelelement.

Some medical device assembly embodiments include connecting the swivelelement to the tunneler.

In some medical device assembly embodiments, the tunneler compriseseither one of a male coupling element or a female connection element andthe swivel element comprises the other of the male coupling element orthe female connection element, and connecting the swivel element to thetunneler comprises slidably engaging the male coupling element and thefemale connection element.

In some medical device assembly embodiments, connecting the swivelelement to the tunneler comprises engaging a recess or groove about aperimeter of the male coupling element with a detent of the femaleconnection element, the engagement of the recess or groove and thedetent fixing the swivel element to the tunneler while permittingrotation between the tunneler and the swivel element. In some cases, theswivel element is not connected to the tunneler during the passing stepand detaching the tunneling tip comprises detaching the tunneling tipfrom direct attachment to the tunneler.

In some medical device assembly embodiments, the carrier elementcomprises a first holder and a second holder; attaching the elongatedlead element to the carrier element comprises inserting a portion of afirst lead element into the first holder and inserting a portion of asecond lead element into the second holder; and pulling the tunnelercomprises pulling the first and the second lead elements from the secondopening to the first opening in the patient so that the first and thesecond lead elements extend between the second opening and the firstopening in the subcutaneous tunnel.

Some medical device assembly embodiments include making either or bothof the first opening and the second opening with the tunneling tip. Insome medical device assembly embodiments, the first opening is in thehead region of the patient and the second opening is in the chest regionof the patient.

In some medical device assembly embodiments, the elongated lead elementcomprises a lead extension having a proximal end and a distal end, andthe method comprises: connecting a lead to the lead extension byinserting a proximal end of the lead into the distal end of the leadextension, and connecting the lead extension to an electricalimplantable medical device by inserting the proximal end of the leadextension into the electrical implantable medical device.

Various embodiments concern a medical device for implanting an elongatedlead element within a subcutaneous tunnel of a patient, comprising, atunneler configured to span between a first opening in the patient and asecond opening within the subcutaneous tunnel; a carrier elementconfigured to attach to the lead extension; and means for linking thecarrier element to the tunneler to allow the tunneler to pull theelongated lead element from the second opening to the first opening sothat the elongated lead element extends from the second opening to thefirst opening in the subcutaneous tunnel while permitting free rotationbetween the carrier element and the tunneler, and for unlinking of thecarrier element from the tunneler.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description of various embodiments of the disclosurein connection with the accompanying drawings, in which:

FIG. 1 is a schematic side view of a system including a lead extensionfor operably coupling a lead to an implantable electrical medicaldevice;

FIG. 2 is a schematic drawing of a system implanted in a patient, wherethe system includes a lead, a lead extension, and an implantableelectrical medical device;

FIG. 3 is a schematic drawing of a tunneler inserted into a patient;

FIG. 4 is a schematic cross-sectional view of an illustrative carrierelement;

FIG. 5 is a schematic view of fixing the carrier element to the leadextension;

FIG. 6 is a schematic drawing of the carrier element being fixed to thelead extension;

FIG. 7 is a schematic drawing of the lead extension placed into apatient spanning two surgical openings in the body with the tunneler;

FIG. 8 is a schematic cross-sectional view of an illustrative dualcarrier element;

FIG. 9 is a flow diagram of an illustrative method;

FIG. 10 is a schematic exploded perspective view of an illustrativeswivel element and tunneler;

FIG. 11 is a schematic perspective view of the illustrative swivelelement of FIG. 10 fixed to the tunneler;

FIG. 12 is a schematic cross-sectional view of an illustrative swivelelement fixed to the tunneler;

FIG. 13 is a cross-sectional view of an illustrative carrier elementthreadedly engaged with the swivel element;

FIG. 14 is a schematic drawing of a carrier element; and

FIG. 15 is a flow diagram of an illustrative method.

The drawings are not necessarily to scale. Like numbers used in thefigures refer to like components, steps and the like. However, it willbe understood that the use of a number to refer to a component in agiven figure is not intended to limit the component in another figurelabeled with the same number. In addition, the use of different numbersto refer to components is not intended to indicate that the differentnumbered components cannot be the same or similar.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanying setof drawings that form a part hereof and in which are shown by way ofillustration several specific embodiments. It is to be understood thatother embodiments are contemplated and may be made without departingfrom the scope or spirit of the present disclosure. The followingdetailed description, therefore, is not to be taken in a limiting sense.The definitions provided herein are to facilitate understanding ofcertain terms used frequently herein and are not meant to limit thescope of the present disclosure.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” encompass embodiments having pluralreferents, unless the content clearly dictates otherwise. As used inthis specification and the appended claims, the term “or” is generallyemployed in its sense including “and/or” unless the content clearlydictates otherwise.

Lead extensions can be placed in a patient by forcing a tunneling devicethrough the patient body between two surgical openings in the body toform a subcutaneous tunnel (e.g., between the head and chest where alead and IPG are respectively being implanted). Then a lead extension isdisposed in a carrier on the tunneling device and pulled back throughthe subcutaneous tunnel, leaving the lead extension in the patient bodyand spanning the two surgical openings in the body. Then both theelectrical lead and the active implantable electrical medical device canbe electrically coupled to the lead extension to complete the procedure.As used herein, elongated lead element refers to one or both of a leadand a lead extension.

Resistance can be experienced as a result of engagement between theassembly and the walls of the subcutaneous tunnel. In particular, largerprofile portions of the assembly can increase resistance. This includesembodiments where a lead extension is linked to a tunneler by a cradlethat surrounds a portion of the lead extension. In some patients,resistance can be experienced while removing the tunneling device withthe lead extension when the lead extension tangles within a subcutaneoustunnel. Enhanced force to remove the tunneling device with the leadextension can result in carrier failure.

The present disclosure describes, among other things, apparatuses andmethods that provide for easy and robust attachment of a medical deviceto a tunneler and robust placement of the medical device (e.g.,elongated lead element) in a patient. Some apparatuses and methodsprovide for robust placement of a lead extension in a patient whileminimizing the profile moved through the subcutaneous tunnel. Theapparatuses and methods described herein may be used in placing nearlyany elongated lead element that is used with an implantable electricalmedical device. A carrier element is disposed at a distal end of atunneler. The carrier element is configured to be slidably disposedwithin a lead connection lumen and a fixation mechanism (e.g., a setscrew, a spring mechanism such as a BAL SEAL™, wiper seal, frictionalengagement member, shape memory engagement member, or other mechanismfor fixing a lead end to a lead extension) of a lead extension isutilized to fix the lead extension to the carrier element. By providingthe carrier portion of the tunneler that can be disposed within a leadconnection lumen of a lead extension, a robust medical device assemblyis formed that can pull an elongated lead element through a subcutaneoustunnel while minimizing the overall outer profile of the assembly withinthe subcutaneous tunnel. The carrier element of the tunneler and thelead extension can be unfixed by the fixation mechanism, such asdisengagement between the set screw and the carrier element orovercoming the resistance or a seal or other engagement member. Thecarrier element can then be removed from the lead connection lumen and aproximal end of a lead can be inserted into the lumen and fixed to thelead extension with the fixation mechanism, such as a set screw or seal.The carrier element can also be fixed to two lead extensions to providefor placement of two lead extensions in the patient. While the presentdisclosure is not so limited, an appreciation of various aspects of thedisclosure will be gained through a discussion of the examples providedbelow. Use of an internal carrier element to implant a lead extension isprincipally described herein, although it is noted that the disclosedapparatuses and methods can be applied to implantation of otherelongated lead elements, such as a lead that is used with or without alead extension.

Some embodiments concern a swivel element on the tunneler, where anelongated lead element can be robustly attached to the swivel end andcan place the elongated lead element in a patient in a manner thatminimizes the risk of lead entanglement during withdrawal of the medicaldevice assembly through a subcutaneous tunnel in the patient. The swivelelement can allow the elongated lead element to rotate independently ofa tunneler handle and can reduce the possibility of entanglement. Theswivel element can reduce the twists in the implanted lead extension andthus reduce residual stresses and latent reliability issues.

Lead extensions of any suitable system employing a lead extension foroperably coupling a lead to an implantable electrical medical device orany other elongated lead element may be placed in accordance with theteachings presented herein. For example, a lead extension may beassociated with an implantable medical device, such as a hearingimplant; a cochlear implant; a sensing or monitoring device; a signalgenerator such as a cardiac pacemaker or defibrillator, aneurostimulator (such as a spinal cord stimulator, a brain or deep brainstimulator, a peripheral nerve stimulator, a vagal nerve stimulator, anoccipital nerve stimulator, a subcutaneous stimulator, etc.), a gastricstimulator; or the like. For the purposes of convenience and brevity,the processes and apparatuses will he described in the context ofreplacement of a lead extension in a DBS system. However, it will beunderstood that the apparatuses and methods described herein may beemployed with regard to replacement of any elongated lead element innearly any implanted system.

Referring to FIG. 1, a schematic view of an example of an implantableelectrical system 101 is shown. In the system shown in FIG. 1,implantable pulse generator (IPG) 200 includes a connector header 240configured to receive male connector 350 at proximal end of leadextension 300. It will be understood that IPG 200 need not have aseparate header 240 to receive extension 300. The distal end ofextension 300 includes a lead receptacle 310 configured to receiveproximal end of lead 400.

Receptacle 310 has internal electrical contacts 370 configured toelectrically couple lead extension 300 to lead 400 via electricalcontacts 480 disposed on the proximal end portion of lead 400. Thereceptacle 310 has a lead connection lumen that is configured to accepta proximal portion of the lead 400 and electrically couple to electricalcontacts 480. The receptacle 310 has one or more lead extension setscrews that are configured to fix the receptacle 310 to the lead 400.

Electrodes 490 are disposed on distal end portion of lead 400 and areelectrically coupled to electrical contacts 480, typically throughinternal conductors (not shown). Lead 400 may include any number ofelectrodes 490, e,g one, two, three, four, five, six, seven, eight,sixteen, thirty-two, or sixty-four. Typically, each electrode 490 iselectrically coupled to a discrete electrical contact 480.

By way of example and referring to FIG. 2, a deep brain stimulation(DBS) system is shown implanted in a patient. For DBS, an IPG 200 can beplaced in the abdominal region of patient, the cranial region, or in thepectoral region as shown. The IPG 200 may be placed in any medicallyacceptable location of the patient. The distal end of the lead 400containing electrodes is placed at a desired location in the patient'sbrain. The proximal end of the lead 400 is inserted into a receptacle310 of the lead extension 300, which is connected to the IPG 200. Onceinserted, one or more lead extension set screws are engaged to fix thereceptacle 310 to the lead 400. Thus, the lead extension 300 couples thelead 400 to the IPG 200. IPG 200 is capable of generating electricalsignals that may be applied to tissue of a patient via the electrodes aspart of therapy. It will be understood that a lead 400, lead extension300, elongated lead element, or system may be used for purposes ofapplying electrical signals to tissue of a patient or for sensingsignals from tissue of a patient.

Implantation of the lead extension 300 requires tunneling between alocation in proximity to the location of a proximal end of the lead 400to a location in proximity to the implant location of the IPG 200, whichin the example of FIG. 2 includes tunneling from the head through theneck to the chest of the patient. A tunneling tool 100 is used to createa subcutaneous path between the implant location of the IPG 200 andimplant location of the proximal end of the lead 400, the lead extension300 being pulled through the tunneled path.

FIG. 3 is a schematic drawing of a tunneler 100 inserted into a patient.The tunneler 100 includes a handle 110 at a proximal end and a tunnelingtip 120 connected to a distal end. The tunneling tip 120 forms thetunnel through the patient body between a first opening 500 (e.g., anincision) and a second opening 510. The tunneler 100 is inserted intothe first opening 500 and forced through the patient body to the secondopening 510. In some cases, the tunneler 100 is used to make either orboth of the first opening 500 and the second opening 510 in someembodiments, a swivel element (described below) connects the tunnelingtip 120 to the distal end of the tunneler 100.

In some embodiments, once the tunneling tip 120 exits the second openingor incision 510, the tunneling tip 120 is replaced with the leadextension carrier element 130. In some embodiments, the tunneling tip isthe lead extension carrier element, as described below. The tunneler 100is a relatively rigid rod or element that is stiff enough to be pushedthrough tissue to form the tunnel in the patient. However the tunneler100 can be flexible enough to bend as required by the operator.

FIG. 4 is a schematic cross-sectional view of an illustrative carrierelement 130. FIG. 5 is a schematic view of fixing the carrier element tothe lead extension. FIG. 6 is a schematic drawing of the carrier element130 being fixed to the lead extension. The internal electrical contactsin the lead connection lumen 313 are not shown.

The lead extension carrier element 130 can be fixed to the tunneler 100in any useful manner. In some embodiments the lead extension carrierelement 130 can be threaded onto the tunneler 100 or the lead extensioncarrier element 130 can be threadedly fixed to the distal end of thetunneler 100.

In some embodiments, the lead extension carrier element 130 is fixedpermanently to the tunneler 100. For example, the lead extension carrierelement 130 and the tunneler 100 may be made from the same material(e.g., both machined from a metal rod or molded as a single polymerunit) or may be welded or adhered to one another. If the lead extensioncarrier element 130 is fixed permanently to the tunneler 100, then thecarrier element 130 may comprise a distal tip 135 as a tunneling tipthat has a point configured to make a subcutaneous tunnel or the carrierelement 130 may be placeable over a tip of the tunneler that isconfigured to make the subcutaneous tunnel, where in the latter case thecarrier element 130 may comprise a proximal end lumen to accommodate thetip of the tunneler 100 when the carrier element 130 is placed over thetip and attached (e.g., by threading) to the tunneler 100. The carrierelement 130 is configured to be slidably disposed within a leadconnection lumen 313. In some embodiments the lead extension carrierelement 130 circumferentially fills the entire or substantially all ofthe lead connection lumen 313, circumferentially in that the width ofthe lead connection lumen 313 is occupied by the lead extension carrierelement 130, although the entire length of the lumen is not necessarilyfilled by the lead extension carrier element 130. The lead extensioncarrier element 130 circumferentially filling the entire orsubstantially all of the lead connection lumen 313 can seal the distalmouth of the lumen to block bodily fluids from entering the leadconnection lumen 313 when these components are brought through thetunnel and then are disengaged, which can protect electrical connectionsthat are later established between electrical conductors on the proximalend of the lead 400 and within the lead connection lumen 313.

Once the carrier element 130 is disposed in the lead connection lumen313, the carrier element 130 is fixed to the receptacle 310 of the leadextension 300 with one or more lead extension set screws 311, 312. Ascrewdriver 590 can be used to rotate the set screws 311. 312 and fixthe carrier element 130 to the receptacle 310 of the lead extension 300.

The carrier element 130 can be an elongated rod that extends from aproximal end 134 to a distal tip 135. The proximal end 134 is fixed tothe tunneler 100 and the distal tip 135 slides into the lead connectionlumen 313. In some embodiments the carrier element 130 is an elongatedrigid rod that is firmed from metal or stiff plastic.

The carrier element 130 includes a plurality of recesses 131, 132 thatare configured to engage with the lead extension set screws 311, 312. Insome embodiments, the plurality of recesses 131, 132 are placed alongthe length of the carrier element 130 so that they mate with one or moreof the lead extension set screws 311, 312 when the carrier element 130is filly disposed in the lead connection lumen 313.

In some embodiments the recesses 131, 132 have a planar bottom surface136 that engages with the lead extension set screws 311, 312. While tworecesses 131, 132 are illustrated, it is understood that any number ofrecesses are contemplated and can mate with and equal the number of leadextension set screws.

Once the lead extension set screws 311, 312 engage the plurality ofrecesses 131, 132 and fix the receptacle 310 of the lead extension 300with the carrier element 130, then the tunneler 100 can be pulled backthrough the tunnel previously formed in the patient body from the secondopening or incision 510 to the first opening or incision 500.

FIG. 7 is a schematic drawing of the lead extension placed into apatient with the tunneler 100. The tunneler 100 is pulled from thepatient through the first and second incisions 500, 510 drawing the leadextension 300 through the subcutaneous path previously occupied by thetunneler 100. The lead extension set screws are then disengaged from theplurality of recesses releasing the receptacle 310 of the lead extension300 from the carrier element 130.

Then the lead 400 is connected to and secured within the lead receptacle310 of the replacement lead extension 300 which has been pulled throughthe patient a sufficient distance to provide access to the leadreceptacle 310 through the incision 500. The lead extension 300 can thenbe connected to the IPG 200. The IPG 200 and connected portions of thelead extension 300 may be implanted in the patient through the incision510.

FIG. 8 is a schematic cross-sectional view of an illustrative dualcarrier element 150. The dual carrier element 150 can be fixed to thetunneler 100 in any useful manner, as described above. The dual carrierelement 150 includes a first carrier element 130 and a second carrierelement 180 fixed to a common hub 151. The common hub 151 fixes the dualcarrier element 150 to the tunneler 100. The operation and function ofthe first carrier element 130 and a second carrier element 180 are thesame as described above for the carrier element 130.

In some embodiments a first carrier element 130 and a second carrierelement 180 are parallel extending elongated rods. In some embodimentsthe first carrier element 130 and a second carrier element 180 arelaterally offset from one another so that the receptacle of each leadextension is laterally off-set from the other. This configuration canallow for a low-profile design and reduce a pulling force required topull the lead extensions back through the subcutaneous tunnel.

The first carrier element 130 is configured to be slidably disposedwithin a first lead connection lumen. In some embodiments the first leadextension carrier element 130 fills the entire or substantially all ofthe first lead connection lumen. Once the first carrier element 130 isdisposed in the first lead connection lumen, the first carrier element130 is fixed to the receptacle of the first lead extension with one ormore lead extension set screws, as described above.

The first carrier element 130 includes a plurality of recesses 131, 132that are configured to engage with the first lead extension set screws,as described above. In some embodiments, the plurality of recesses 131,132 are placed along the length of the first carrier element 130 so thatthey mate with one or more of the first lead extension set screws whenthe first carrier element 130 is fully disposed in the lead connectionlumen. In some embodiments, the first carrier element 130 includes astop element 139 that stops the advancement of the first lead extensionon the first carrier element 130. The stop element 139 can be placed sothat the plurality of recesses 131, 132 align with one or more of thelead extension set screws when the first lead extension is advanced ontothe first carrier element 130 to the stop element 139. The embodiment ofFIG. 4 could likewise include a stop element placed so that theplurality of recesses 131, 132 align with the lead extension set screws311, 312 when the lead receptacle 310 is advanced onto the carrierelement 130 to the stop element. In some embodiments similar to that ofFIG. 4, the carrier element 130, recesses 131, 132, and proximal end 134are spaced such that the lead receptacle 310 is stopped by contact withthe proximal end 134 thereby aligning the plurality of recesses 131, 132and the lead extension set screws 311, 312 when the carrier element 130is slid into the lead receptacle 310.

In some embodiments the recesses 131, 132 have a planar bottom surface136 that engages with the lead extension set screws, as described above.While two recesses 131, 132 are illustrated, it is understood that anynumber of recesses are contemplated and can mate with and equal thenumber of lead extension set screws.

The second carrier element 180 is configured to be slidably disposedwithin a second lead connection lumen. In some embodiments the secondlead extension carrier element 180 fills the entire or substantially allof the second lead connection lumen. Once the second carrier element 180is disposed in the second lead connection lumen, the second carrierelement 180 is fixed to the receptacle of the second lead extension withone or more lead extension set screws, as described above.

The second carrier element 180 includes a plurality of recesses 181, 182that are configured to engage with the second lead extension set screws,as described above. In some embodiments, the plurality of recesses 181,182 are placed along the length of the second carrier element 180 sothat they mate with one or more of the second lead extension set screwswhen the second carrier element 180 is fully disposed in the second leadconnection lumen. In some embodiments, the second carrier element 180includes a stop element 189 that stops the advancement of the secondlead extension on the second carrier element 180. The stop element 189can be placed so that the plurality of recesses 181, 182 align with oneor more of the lead extension set screws when the lead extension isadvanced onto the carrier element 180 to the stop element 189.

In some embodiments the recesses 181, 182 have a planar bottom surface186 that engages with the lead extension set screws, as described above.While two recesses 181, 182 are illustrated, it is understood that anynumber of recesses are contemplated and can mate with and equal thenumber of lead extension set screws.

Once the lead extension set screws of both the first and second leadextensions engage the plurality of recesses 131, 132, 181, 182 and fixthe receptacles of the first and second lead extensions with the carrierelements 130, 180 then the tunneler 100 can be pulled back through thetunnel previously formed in the patient body from the second opening orincision to the first opening or incision, leaving the first and secondlead extensions in the subcutaneous tunnel spanning between the firstopening or incision 500 and the second opening or incision 510.

FIG. 9 is a flow diagram of an illustrative method 600. The method forimplanting a lead extension in a patient includes pushing or passing atunneler from a first opening to a second opening in a patient at box610. Then the method includes fixing a carrier portion or carrierelement on a distal end of the tunneler at box 620. A tunneling tip canbe removed from the tunneler and then the carrier portion can be fixedto the tunneler distal end by any useful manner, such as threading thecarrier element or portion onto the tunneler. The carrier portion orelement is configured to slide into the lead extension lumen.

The method includes disposing or sliding a lead connection lumen of alead extension onto the carrier element at box 630 and fixing the leadextension to the carrier element with a set screw (or other fixationmechanisms) on the lead extension at box 640. The set screw (or otherfixation mechanism) can align with a recess on the carrier element tosecurely fix the carrier element to the lead extension and provide arobust and secure connection; however it is noted that the carrierelement may be generally straight (i.e. no recesses) in some embodimentsand the set screw may be pressed onto the flat carrier element byscrewing action to secure the carrier element to the lead extension byfriction between the set screw and carrier element. The method thenincludes pulling the tunneler and secured lead extension from the secondopening to the first opening in the patient at box 650 and removing thelead extension from the carrier portion at box 660 after set screws orother securement means have been released. A proximal end of a lead canthen be inserted into the lead extension lumen. The lead can have anumber of external contacts spaced on the proximal end of the lead thatare electrically connected with electrodes on the distal end of lead.Inserting of the proximal end of a lead into the lead extension lumencan engage the contacts of the lead with electrical connectors withinthe lead extension lumen that are spaced to respectively connect withthe contacts of the lead, thereby completing electrical connectionsbetween conductors of the extension and distal end electrodes of thelead. The set screws (or other fixation mechanisms) can again be engaged(e.g., screwed) in to fix the lead extension to the lead. In the case ofset screws, the set screws apply pressure to the lead (e.g., on thecontacts) or engaging a recess of the lead. The electrical connectionsmay be made active when an IPG is connected to the proximal end of thelead extension and electrical energy is delivered from the IPG to thedistal end electrodes of the lead for stimulation of tissue proximatethe distal end electrodes.

If a dual carrier element is utilized (e.g., see FIG. 8) the method 600includes disposing a distal end first carrier portion of the tunnelerinto a first lead connection lumen of a first lead extension anddisposing a distal end second carrier portion of the tunneler into asecond lead connection lumen of a second lead extension. The firstcarrier portion and the second carrier portion are fixed to a common huband the common hub is fixed to the distal end of the tunneler. The firstlead extension has a set screw proximal to the first lead connectionlumen and the second lead extension has a set screw proximal to thesecond lead connection lumen.

In various embodiments, a swivel element can be employed on a tunnelingtool. The swivel element can allow free rotation between the elongatedlead element (e.g., a lead or extension) and a tunneling tool while theelongated lead element is withdrawing by the tunneling tool back throughthe patient. The swivel elements can allow the elongated lead element toconfirm and move with the path of the tunnel and twist within the tunnelwithout building up twists within the elongated lead element.Specifically, the possibly irregular path of the tunnel may cause theelongated lead element to twist as the elongated lead element is broughtthrough the tunnel. These twists can cause the elongated lead element tobecome wound up within the tunnel, causing stress and tension along theimplanted lead. The swivel element can allow the elongated lead elementto twist to conform to the possibly irregular path of the tunnel andease the pulling of the elongated lead element through the tunnelwithout building up one or more twists of the lead material.

Various embodiments can have a swivel feature. Returning to FIG. 3,where the tunneling tip 720 exits the second opening 510, the tunnelingtip 720 may be replaced with a swivel element that complements or is analternative to the carrier element previously discussed. In someembodiments, the tunneling tip 720 is removed from the swivel element byholding the tunneling tip 720 and rotating the swivel element, where inthis case the swivel element is permanently part of the tunneler 100.

FIG. 10 is a schematic exploded perspective view of an illustrativeswivel element 700 and tunneler 100. FIG. 11 is a schematic perspectiveview of the illustrative swivel element 700 of FIG. 10 fixed to thetunneler 100. FIG. 12 is a schematic cross-sectional view of anillustrative swivel element 700 fixed to the tunneler 100. A tunnelingtip 720 is illustrated as being fixed to the distal end of the swivelelement 700 in FIG. 10 and FIG. 11.

The swivel element 700 can be fixed to the distal end of the tunneler100 via any useful manner that maintains axial rotation of the swivelelement 700 relative to the tunneler 100 without the rotation separatingthe swivel element 700 from the tunneler 100 (e.g., not mere threadingthat can be unscrewed with a few turns). Generally, the swivel element700 can rotate in both clockwise and counter-clockwise directionsrelative to the tunneler 100. In some embodiments the tunneler 100includes a male coupling element 725 that has a reduced diameterrelative to the tunneler 100 and a detent engagement recess or groove726 about a perimeter of the male coupling element 725.

The swivel element 700 proximal end can include a female connectionelement that is configured to mate with the male coupling element 725 ofthe tunneler 100. The swivel element 700 can slidably engage the malecoupling element 725. In some embodiments, a detent element 736 canengage the detent engagement recess or groove 726 of the male couplingelement 725. The engagement of the detent element 736 with the detentengagement recess or groove 726 fixes the swivel element 700 to thetunneler 100 while allowing the swivel element 700 to rotate freelyabout the male coupling element 725 of the tunneler 100 (e.g., by havingthe recess or groove 726 extend all the way around (i.e. 360 degrees)the male coupling element 725). The outer surface 734 of the swivelelement 700 can have a roughened surface or a knurled surface to assistin grasping and rotating the swivel element 700.

The tunneling tip 720 can be removed by rotating the swivel element 700and disengaging the threaded end 735 of the swivel element 700 from thethreaded end of the tunneling tip 720. The distal end of the swivelelement 700 can include a threaded portion to threadedly engage amedical device, carrier element, or other medical element, as desired.The threaded portion can be a male threaded end or a female threadedend. FIG. 11 shows the tunneling tip 720 engaged with the swivel element700 while FIG. 6 shows the swivel element 700 in a state where thetunneling tip 720 has been unthreaded from female threaded end 735 andremoved from the swivel element 700.

FIG. 13 is a cross-sectional view of an illustrative carrier element 740threadedly engaged with the swivel element 700. The carrier element 740can be fixed to the distal end of the swivel element 700 by rotating(see arrow) the swivel element 700 relative to the carrier element 740.The illustrated embodiment shows a lead extension carrier element 740having a male threaded end 745 threadedly engaged with a female threadedend 735 of the swivel element 700. In some other embodiments the carrierelement 740 has a female threaded end threadedly engaged with a malethreaded end of the swivel element 700.

FIG. 14 is a drawing of a carrier element 740. A proximal end 750 of thecarrier element 740 can be threaded, as shown by male threaded end 745in FIG. 13, to attach the carrier element 740 to the swivel element 700.In the embodiment of FIG. 14, the carrier element 740 includes a holder760. The holder 760 interior is configured to fit an end of the leadextension 300, such as the lead receptacle 310 on the distal end of thelead extension 300 illustrated in FIG. 9, to secure the lead extension300 to the carrier element 740 and thereby link the lead extension 300to the swivel element 700 and the tunneler 100. The carrier element 740includes a narrow end 770 which can be narrower than the width of thedistal end of the lead extension 300 (the holder 760 being dimensionedto seat the lead receptacle 310) but wider than the elongated middleportion of the lead extension 300, allowing the elongated middle portionof the lead extension 300 to extend out of the narrow end 770 distallyof the carrier element 740. In this way, the carrier element 740 cansecurely harness a distal end of the lead extension 300 and allow therest of the lead extension 300 to be pulled behind the carrier element740 as the tunneler 100 pulls the swivel element 700, carrier element740, and lead extension 300 through a subcutaneous tunnel

The carrier element 740 may contain multiple holder compartments forattaching multiple (e.g., two) lead extensions simultaneously andpulling both lead extensions through a subcutaneous tunnel. For example,a second holder can be included on the underside of the carrier element740 proximal to the first holder 760, with the narrow end 770 includingtwo narrowed sections for harnessing the respective distal ends of thetwo lead extensions while allowing the elongated middle sections of thelead extensions to extend from the carrier element 740. In someembodiments, the carrier element 740 is configured to be slidablydisposed within a lumen of the distal end of the lead extension 300,such as a lumen in the receptacle 310. Once the carrier element 740 isdisposed in the lumen, the carrier element 740 is fixed to the leadextension 300 with one or more lead extension set screws that screw downand engage the carrier element 740 or by some other fixation mechanism.In sonic embodiments the carrier element 740 is an elongated rigid rodthat is formed from metal or stiff plastic.

Once the lead extension 300 is attached to the carrier element 740, thenthe tunneler 100 can be pulled back through the tunnel previously formedin the patient body from the second opening or incision 510 to the firstopening or incision 500 such that the lead extension 300 spans betweenthe first and the second openings. The receptacle of the lead extension300 is then released from the carrier element 740 (e.g., removed fromthe holder 760) thereby uncoupling the tunneler 100 from the leadextension 300. The lead 400 can be connected to the lead extension 300in the same manner as FIG. 7 or as otherwise described herein.

FIG. 15 is a flow diagram of an illustrative method 800. The method 800for implanting a lead extension in a patient includes pushing or passinga tunneler with a swivel element from a first opening to a secondopening in a patient at box 810 to make a subcutaneous tunnel. Atunneling tip can be attached (e.g., by threaded engagement) to thedistal end of the swivel element, the tunneling tip tapered to separatetissue and make the subcutaneous tunnel In some embodiments, the swivelelement is not attached to the tunneler during the pushing/passing stepat box 810 and instead the tunneling tip is attached directly to thetunneler (e.g., by slidably engaging a female connection element with amale coupling element in similar manner to that of FIG. 15).

In some embodiments, a tunneling tip is removed from the distal end ofthe tunneler (e.g., by rotation to unthread a coupling between thetunneling tip and the swivel element) as the tunneling tip extends outof the second opening. Then, while the swivel element extends out of thesecond opening, the swivel element can be rotated to attach a carrierelement to the tunneler at box 820. The method optionally includesfixing a lead extension about the carrier element at box 830. The methodincludes pulling the lead extension from the second opening to the firstopening in the patient with the tunneler and swivel element at box 840.The method optionally includes rotating the swivel element to detach theswivel element from the carrier element from the tunneler at box 850.

Thus, embodiments of the MEDICAL TUNNELING DEVICE AND METHOD aredisclosed. The implementations described above and other implementationsare within the scope of the following claims. One skilled in the artwill appreciate that the present disclosure can be practiced withembodiments other than those disclosed. The disclosed embodiments arepresented for purposes of illustration and not limitation, and thepresent invention is limited only by the claims that follow.

What is claimed is:
 1. A method for implanting a lead extension having alead connection lumen in a subcutaneous tunnel comprising: passing atunneler from a first opening to a second opening in a patient, asubcutaneous tunnel being made by the passing of the tunneler; disposinga distal end carrier portion of the tunneler into the lead connectionlumen of the elongated lead element, the elongated lead element; fixingthe lead extension to the distal end carrier portion with a fixationmechanism; pulling the tunneler and attached lead extension from thesecond opening to the first opening in the subcutaneous tunnel so thatthe lead extension extends between the second opening and the firstopening; unfixing the lead extension from the distal end carrier portionwith the fixation mechanism; removing the distal end carrier portionfrom the lead connection lumen; and connecting a lead to the leadextension by inserting a proximal end of the lead into the leadconnection lumen and securing the lead to the lead extension with thefixation mechanism, the connecting of the lead to the lead extensioncompleting at least one electrical connection between one or moreelectrical conductors of the lead extension and one or more electrodeson the distal end of the lead.
 2. The method according to claim 1further comprising: removing a tunneling tip from the distal end of thetunneler after the passing step but before the disposing step, thetunneling tip configured to make the tunnel in subcutaneous tissue; andfixing the carrier portion to the distal end of the tunneler after theremoving step.
 3. The method according to claim 1, wherein: fixing thelead extension to the distal end carrier portion comprises engaging thedistal end carrier portion with a set screw; and unfixing the leadextension from the distal end carrier portion comprises disengaging thedistal end carrier portion from the set screw.
 4. The method accordingto claim 1 wherein the distal end carrier portion is able to freelyrotate relative to a handle on a proximal end of the tunneler.
 5. Themethod according to claim 1 wherein the tunneler creates one or both ofthe first opening and the second opening.
 6. The method according toclaim 1 wherein: the distal end carrier portion comprises a firstcarrier element and a second carrier element, the first and secondcarrier elements connected to a common hub; the lead extension comprisesa first lead extension having a first lead connection lumen and a secondlead extension having a second lead connection lumen; the lead comprisesa first lead having a proximal end and a distal end and a second leadhaving a proximal end and a distal end; disposing comprises disposingthe first carrier element in the first lead connection lumen anddisposing the second carrier element in the second lead connectionlumen; pulling the tunneler and attached lead extension comprisespulling the tunneler and both of the first and second lead extensionsfrom the second opening to the first opening in the patient so that thefirst and second lead extensions extend between the second opening andthe first opening in the patient; unfixing the lead extension comprisesunfixing the first and second lead extensions from the first and thesecond carrier elements; removing the distal end carrier portioncomprises removing the first and the second carrier elements from thefirst and the second lead extension lumens; and connecting the lead tothe lead extension comprises inserting the proximal end of the firstlead into the first lead connection lumen, securing the first lead tothe first lead extension with a first set screw, inserting the proximalend of the second lead into the second lead connection lumen, andsecuring the second lead to the second lead extension with a second setscrew.